Field of the Invention
The invention relates to a power conversion technique, and more particularly, to an inverting apparatus and a control method thereof.
Description of Related Art
A typical inverting apparatus is applied in a photovoltaic grid system, and an electromagnetic interference (EMI) filter circuit is disposed at the back-end of the inverting apparatus and connected to a power grid. After using a DC-to-AC inverting apparatus to convert the DC power of a photovoltaic device to an AC power, the photovoltaic grid system outputs an AC current to the EMI filter circuit for filtering and then providing to the power grid.
The EMI filter circuit is generally provided with a safety capacitor (i.e., an X capacitor) to perform filtering. Although the safety capacitor can filter and remove high-frequency EMI, it may also cause a portion of the AC current outputted by the inverting apparatus to be consumed by the safety capacitor at the same time (i.e., imaginary current of safety capacitor). As a result, the amplitudes/phases of the AC current received by the power grid and the AC current outputted by the inverting apparatus do not match, thus reducing the power factor of the inverting apparatus.